• Bulletin of the Korean Chemical Society
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• 제10권4호
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• pp.382-388
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• 1989

The approximate rates and stoichiometry of the reaction of excess potassium tri-sec-butylborohydride ($K_s-Bu_3BH$) with selected organic compounds containing representative functional groups were determined under the standard conditions (0$^{\circ}C$, THF) in order to define the characteristics of the reagent for selective reductions. Primary alcohols evolve hydrogen in 1 h, but secondary and tertiary alcohols and amines are inert to this reagent. On the other hand, phenols and thiols evolve hydrogen rapidly. Aldehydes and ketones are reduced rapidly and quantitatively to the corresponding alcohols. Reduction of norcamphor gives 99.3% endo- and 0.7% exo-isomer of norboneols. The reagent rapidly reduces cinnamaldehyde to the cinamyl alcohol stage and shows no further uptake of hydride. p-Benzoquinone takes up one hydride rapidly with 0.32 equiv hydrogen evolution and anthraquinone is cleanly reduced to the 9,10-dihydoxyanthracene stage. Carboxylic acids liberate hydrogen rapidly and quantitatively, however further reduction does not occur. Anhydrides utilize 2 equiv of hydride and acyl chlorides are reduced to the corresponding alcohols rapidly. Lactones are reduced to the diol stage rapidly, whereas esters are reduced moderately (3-6 h). Terminal epoxides are rapidly reduced to the more substituted alcohols, but internal epoxides are reduced slowly. Primary and tertiary amides are inert to this reagent and nitriles are reduced very slowly. 1-Nitropropane evolves hydrogen rapidly without reduction and nitrobenzene is reduced to the azoxybenzene stage, whereas azobenzene and azoxybenzene are inert. Cyclohexanone oxime evolves hydrogen without reduction. Phenyl isocyanate utilizes 1 equiv of hydride to proceed to formanilide stage. Pyridine and quinoline are reduced slowly, however pyridine N-oxide takes up 1.5 equiv of hydride in 1 hr. Disulfides are rapidly reduced to the thiol stage, whereas sulfide, sulfoxide, sulfonic acid and sulfone are practically inert to this reagent. Primary alkyl bromide and iodide are reduced rapidly, but primary alkyl chloride, cyclohexyl bromide and cyclohexyl tosylate are reduced slowly.

• Archives of Pharmacal Research
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• 제27권7호
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• pp.683-692
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• 2004

Curcumin (diferuloylmethane) is a major naturally-occurring polyphenol of Curcuma species, which is commonly used as a yellow coloring and flavoring agent in foods. Curcumin has shown anti-carcinogenic activity in animal models. Curcumin possesses anti-inflammatory activity and is a potent inhibitor of reactive oxygen-generating enzymes such as lipoxygenase/cyclooxygenase, xanthine dehydrogenase/oxidase and inducible nitric oxide synthase; and an effective inducer of heme oxygenase-1. Curcumin is also a potent inhibitor of protein kinase C(PKC), EGF(Epidermal growth factor)-receptor tyrosine kinase and LĸB kinase. Subsequently, curcumin inhibits the activation of NF(nucleor factor)KB and the expressions of oncogenes including c-jun, c-fos, c-myc, NIK, MAPKs, ERK, ELK, PI3K, Akt, CDKs and iNOS. It is proposed that curcumin may suppress tumor promotion through blocking signal transduction path-ways in the target cells. The oxidant tumor promoter TPA activates PKC by reacting with zinc thiolates present within the regulatory domain, while the oxidized form of cancer chemopreventive agent such as curcumin can inactivate PKC by oxidizing the vicinal thiols present within the catalytic domain. Recent studies indicated that proteasome-mediated degradation of cell proteins playa pivotal role in the regulation of several basic cellular processes including differentiation, proliferation, cell cycling, and apoptosis. It has been demonstrated that curcumin-induced apoptosis is mediated through the impairment of ubiquitin-proteasome pathway. Curcumin was first biotransformed to dihydrocurcumin and tetrahydrocurcumin and that these compounds subsequently were converted to monoglucuronide conjugates. These results suggest that curcumin-glucuronide, dihydrocurcumin-glucuronide, tetrahydrocurcumin-glucuronide and tetrahydrocurcumin are the major metabolites of curcumin in mice, rats and humans.

• Bulletin of the Korean Chemical Society
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• 제13권2호
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• pp.199-207
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• 1992

The approximate rates and stoichiometry of the reaction of excess sodium diethyldihydroaluminate (SDDA) with 68 selected organic compounds containing representative functional groups were examined under standard conditions (THF-toluene, $0^{\circ}C$ in order to compare its reducing characteristics with lithium aluminum hydride (LAH), aluminum hydride, and diisobutylaluminum hydride (DIBAH) previously examined, and enlarge the scope of its applicability as a reducing agent. Alcohols, phenol, thiols and amines evolve hydrogen rapidly and quantitatively. Aldehydes and ketones of diverse structure are reduced rapidly to the corresponding alcohols. Reduction of norcamphor gives 11% exo-and 89% endo-norborneol. Conjugated aldehydes such as cinnamaldehyde are rapidly and cleanly reduced to the corresponding allylic alcohols. p-Benzoquinone is mainly reduced to hydroquinone. Hexanoic acid and benzoic acid liberate hydrogen rapidly and quantitatively, however reduction proceeds very slowly. Acid chlorides and esters tested are all reduced rapidly to the corresponding alcohols. However cyclic acid anhydrides such as succinic anhydride are reduced to the lactone stage rapidly, but very slowly thereafter. Although alkyl chlorides are reduced very slowly alkyl bromides, alkyl iodides and epoxides are reduced rapidly with an uptake of 1 equiv of hydride. Styrene oxide is reduced to give 1-phenylethanol quantitatively. Primary amides are reduced very slowly; however, tertiary amides take up 1 equiv of hydride rapidly. Tertiary amides could be reduced to the corresponding aldehydes in very good yield ( > 90%) by reacting with equimolar SDDA at room temperature. Hexanenitrile is reduced moderately accompanying 0.6 equiv of hydrogen evolution, however the reduction of benzonitrile proceeds rapidly to the imine stage and very slowly thereafter. Benzonitrile was reduced to give 90% yield of benzaldehyde by reaction with 1.1 equiv of hydride. Nitro compounds, azobenzene and azoxybenzene are reduced moderately at $0^{\circ}C$, but nitrobenzene is rapidly reduced to hydrazobenzene stage at room temperature. Cyclohexanone oxime is reduced to the hydroxylamine stage in 12 h and no further reaction is apparent. Pyridine is reduced sluggishly at $0^{\circ}C$, but moderately at room temperature to 1,2-dihydropyridine stage in 6 h; however further reaction is very slow. Disulfides and sulfoxides are reduced rapidly, whereas sulfide, sulfone, sulfonic acid and sulfonate are inert under these reaction conditions.

• Bulletin of the Korean Chemical Society
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• 제8권4호
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• pp.285-291
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• 1987

The approximate rates, stoichiometries and products of the reaction of potassium triethylborohydride $(KEt_3BH)$ with selected organic compounds containing representative functional groups under the standard condition $(0^{\circ}C,$ THF) were examined in order to explore the reducing characteristics of this reagent as a selective reducing agent. Primary alcohols, phenols and thiols evolve hydrogen rapidly whereas secondary and tertiary alcohols evolve very slowly. n-Hexylamine is inert to this reagent. Aldehydes and ketones are reduced rapidly and quantitatively to the corresponding alcohols. Reduction of noncamphor gives 3% exo- and 97% endo-norboneol. Anthraquinone is cleanly reduced to 9,10-dihydro-9,10-dihydroxyanthracene stage. Carboxylic acids liberate hydrogen rapidly and quantitatively but further reduction does not occur. Anhydrides utilize 2 equiv of hydride to give an equimolar mixture of acid and alcohol. Acid chlorides, esters and lactones are rapidly and quantitatively reduced to the corresponding alcohols. Epoxides are reduced at moderate rates with Markovnikov ring opening to give the more substituted alcohols. Primary amides liberate 1 equiv of hydrogen rapidly. Further reduction of caproamide is slow whereas benzamide is not reduced. Tertiary amides are reduced slowly. Benzonitrile utilizes 2 equiv of hydride in 3 h to go to the amine stage whereas capronitrile takes only 1 equiv. The reaction of nitro compounds undergo rapidly whereas azobenzene and azoxybenzene are reduced slowly. Cyclohexanone oxime rapidly evolves hydrogen without reduction. Phenyl isocyanate utilizes 1 equiv of hydride to proceed to formanilide stage. Pyridine N-oxide and pyridine is reduced rapidly. Disulfides are rapidly reduced to the thiol stage whereas sulfoxide, sulfonic acid are practically inert to this reagent. Sulfones and cyclohexyl tosylate are slowly reduced. Octyl bromide is reduced rapidly but octyl chloride and cyclohexyl bromide are reduced slowly.

• 대한의생명과학회지
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• 제4권1호
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• pp.1-9
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• 1998

효모의 티올특이성 항산화단백과 아미노산 서열상 상동성을 보이는 50종류의 단백은 새로운 항산화 단백군을 형성하며 또한 병원성 미생물에도 널리 분포하고 있으나 이들 단백의 생화학적 및 생리적인 기능은 거의 알려져 있지 않은 실정이다. 본 연구는 병원성 미생물의 티올특이성 항산화단백의 기능에 관한 연구로서 Saccharomyces cerevisiae의 TSA 및 Salmonella typhimurium alkcyl hydroperoxide reductase의 AhpC subunit와 상동성을 나타내는 Corynebacterium diphtheriae의 DirA 유전자를 PCR 방법으로 클로닝하고 대장균에 발현시킨 후 정제하여 항산화 특성을 조사하였다. 정제된 DirA는 티올을 함유하는 금속촉매 산화계인 DTT/Fe$^{3+}$를 선택적으로 억제하였으며 티오레독신 의존성 과산화물 분해활성을 나타내었다. DTT/Fe$^{3+}$ 금속촉매 산화계에 의한 효소의 불활성화를 50% 억제 하는 DirA의 농도는 0.12 mg/ml로 효모 TSA 항산화활성의 약1/4 수준이었으며, 효모의 티 오레 독신계와 반응시켰을때 과산화물 분해활성은 0.02 unit/mg로서 효모 TSA의 티오레독신 의존성 과산화물 분해활성의 1/20수준이었다. 정제된 단백질을 이용하여 항체를 제조하였으며 이항체를 이용하여 Corynebacterium diphtheriae에서 발현됨을 확인하였다. 이러한 결과를 통하여 Corynebacterium diphtheriae의 병원성은 숙주세포의 방어기전인 백혈구에 의하여 생성되는 과산화수소 또는 다른 활성산소종을 제거하는 DirA작용과 연관이 있는 것으로 사료된다.